CAIRO (AP) -- Human Rights Watch on Thursday called for an arms embargo on Saudi Arabia over the war in Yemen, and said the United States might be complicit in "atrocities" by supplying bombs.

The New York-based group said more than 160 people were killed in one month, mostly by U.S. bombs sold to the Saudi-led coalition battling Yemen's Houthi rebels. It said the U.S. arms were supplied after earlier violations had been publicized, and were used in airstrikes in September and October.

"The Obama administration is running out of time to completely suspend U.S. arms sales to Saudi Arabia or be forever linked to Yemen wartime atrocities," Human Rights Watch researcher Priyanka Motaparthy said.

A Saudi-led coalition supported by the United States launched an air campaign on behalf of Yemen's internationally recognized government in March 2015. The year before, the Houthis had seized much of northern Yemen, including the capital, Sanaa.

More than 4,000 civilians have been killed in the conflict, and some 3 million have been displaced. The fighting, along with an air and sea blockade by the coalition, has pushed the Arab world's poorest country to the brink of famine.

Rights groups have investigated dozens of airstrikes that targeted weddings, busy markets, hospitals, and schools. They have accused the coalition of committing war crimes and called for an international investigation.

The Human Rights Watch report released Thursday included findings from an investigation into an air raid in Arhab, a town north of Sanaa, on Sept. 10 that killed 31 civilians, including several first responders, and wounded more than 40.

HRW said fragments of the weapons used in the attack show they were produced in the U.S. in October 2015, after several rights groups had already reported alleged violations.

Ten days later, warplanes struck a three-story house near a funeral, killing more than 28 civilians and wounding 32 in the Red Sea port city of Hodeida, the group said.

"Governments selling weapons to Saudi Arabia cannot with any credibility rely on either coalition or Yemeni-led investigations to determine whether these weapons are being used against civilians," Motaparthy said. "The U.S., U.K., and others selling weapons to Saudi Arabia should suspend these sales until unlawful attacks are curtailed and properly investigated."